The Square Kilometre Array
From the deep sea to the deep dark sky above now, and how we know what’s up there. The Square Kilometre Array is a giant readio telescope, and recently Adam Murphy and Ben Mcallister spoke with Phil Diamond, the Director General of the SKA project...
Phil - The science case for SKA, if I may...here it is.
Ben - Hahaha! For audio listeners, Phil has just picked up two very large thick books, the size of two encyclopedias each.
Phil - Yeah. So they actually - they weigh 9.8 kilograms combined.
Adam - Oh, good exercise then. Yeah.
Phil - Yeah. So that's 2000 pages describing the science that astronomers hope to do with the SKA, but in there, we have identified what we call key science programs. So the SKA must be able to deliver these key science projects, as well as do an enormous other range. But at the very least, it must be able to do the key science projects. One is using pulsars, to use pulsars to understand the nature of gravitational waves. A few years ago, LIGO the laser interferometer gravitational wave observatory detected gravitational waves from massive objects coalescing, and emitting gravitational waves across the universe. That's one way of detecting them, another way of detecting gravitational waves from much heavier objects, supermassive black holes at the hearts of galaxies, is by observing the effect of the gravitational waves on the pulsars that sit across the Milky Way, across our galaxy. We'll be using the SKA to monitor the signals coming from a network of pulsars. These are very accurate clocks. Nature's clocks remember, distributed across the sky. And as a gravitational wave crosses our galaxy, it will perturb the clock signals and we'll be able to detect that perturbation, and therefore measure the gravitational wave.
Ben - So like a galaxy wide gravitational wave observatory, as opposed to a few kilometre tunnel?
Phil - Yeah. It's using the galaxy as a telescope, as a detector, which I find mindblowing. Another key area is to use hydrogen. So with the SKA, one of the reasons we're going from 50 megahertz all the way up to 15 gigahertz, is to be able to have that full range of frequency, to detect hydrogen all the way back, almost to the Dawn of the Universe. So we want to see what happens in those early years of the universe. When the universe started to become transparent to radiation, and watch the first stars, the first galaxies evolve all the way up until the present day. So essentially, we'll be acting as a time machine.
Ben - Is the point just that because hydrogen is everywhere in the universe, it's extremely abundant. Being able to see the characteristic, radiation that only hydrogen emits, allows you to see a lot of the interesting structure. And because the signals of the hydrogen in the early universe are still kicking around in the universe, they're just changed a bit, we can still see those really early signals and kind of reconstruct what happened in the early universe?
Phil - No, that's exactly right. Our images of the early universe have come from projects, spacecraft like Planck, an ESA mission that ended a few years ago, or its precursors. These satellites produced snapshots of what the universe looked like when it was about 400,000 years old. Bear in mind, it's almost 14 billion years old now. So we have these snapshots and there's a huge amount of physics being gained from those snapshots of the universe as a baby, as a child, really. And what we want to be able to do with hydrogen, which as you say, is everywhere, is make a movie of the universe, from its childhood, growing up through adolescence, to the mature universe that we now live in. There's going to be some fantastic things come from that, that ability to just observe that time period.
Ben - I can't wait to see what we learn.